How do I smooth out a path
You can just increase the resolution of the curve:

I also see that you are using a NURBS path with several extrusions to form the simple curved road shape. Curves are designed to help artists interpolate between control points so they don't need to manually add dozens or hundreds of them. Try to use as few control points as possible.
I advise you to use bezier curves, as they offer users much more control over the shape. Here is what the road (I assume it is a quarter circle, I might be wrong) would look like. I added a primitive Bezier Circle and deleted the other 3/4ths of it.